Sensors play an important role in a wide variety of devices as sensors can provide critical information concerning the status, operational conditions, performance, wear, safety, and countless other conditions. Strain sensors provide information about a load and serve an important role in monitoring the structural health of structures such as civil engineering structures.
As noted in U.S. Publication Number 20060070451, monitoring load distributions provide information about the forces within a mechanical structure, including bending and twisting, that can be communicated to a monitoring device and provide warnings or historical performance information concerning the safety of a mechanical component.
A strain sensor may be incorporated into an electronic control system that limits some form of operation or applies a corrective load when dangerous conditions are detected by a strain sensor. Limitations of conventional strain sensors include the power consumption needs of the strain sensors, the manner in which the strain sensors may be connected into other systems, the sensitivity and operating range of the sensor, and the size of the strain sensors. Thus, there is a need for a strain sensor that can operate at a higher range of sensitivity, with lower power consumption, in harsh environments, with off-the-shelf electronics, and on a micro-scale.
U.S. Pat. No. 5,786,621, issued Jul. 28, 1998 to Saif et al., describes a micro-scale electromechanical structure incorporating a stable planar frame, to which is connected a multiplicity of comb-type capacitive actuators. The frame is mounted to a substrate by means of arms which position the capacitor plates, and the instrument is calibrated by buckling a beam cofabricated with the instrument, and is used for material structural health monitoring testing, in macroscopic analytical devices, in order to study in-situ the micro-structural changes.
Micro-scale electromechanical structure strain sensors that rely on traditional comb-type structure typically function well under controlled conditions, but less well in harsh environments and may have limited sensitivity and operating range. Thus, there is a need for a micro-scale electromechanical structure strain sensor that can operate at a higher range of sensitivity in harsh environments.